1. Field of the Invention
This invention relates to a vehicle driving system, more particularly to a driving device for adjusting an orientation of a vehicle wheel.
2. Description of the Related Art
FIGS. 1 and 2 show a conventional driving device 5 for adjusting an orientation of a vehicle wheel that is disclosed in U.S. Pat. No. 4,973,070. The driving device 5 is attached to a vehicle body, and includes a motor 1, two screw rods 2 driven by the motor 1, two threaded sleeves 3 respectively and threadedly sleeved around the screw rods 2, and two link rods 4 respectively connecting to the threaded sleeves 3. One of the link rods 4 is connected to the vehicle wheel, and the other one of the link rods 4 is connected to the vehicle body. When the motor 1 is activated, the two link rods 4 are moved toward and away from each other so as to adjust the orientation of the vehicle wheel.
However, since the conventional driving device 5 forms a suspension arm for connecting the vehicle wheel and the vehicle body by combining the motor 1, the screw rods 2, the sleeves 3 and the link rods 4, an unsprung mass of the vehicle is increased. In addition, because the screw rods 2, the link rods 4, and the sleeves 3 cooperatively form a multi-section suspension arm, and because the screws 2 are connected threadedly to the sleeves 3, the robustness of the entire suspension arm is not satisfactory.